Pertussis and inactivated polio vaccines are made from live bacteria or viruses that are killed with formaldehyde. Both tetanus and diphtheria toxins are inactivated with formaldehyde to make the toxoids. Following the inactivation process, purification of the vaccines removes almost all of the formaldehyde. The diphtheria, pertussis, tetanus, polio and Haemophilus b 5-in-1 vaccine contains less than 0.02% formaldehyde per dose, or less than 200 parts per million. This amount of formaldehyde is several hundred times lower than the amount known to cause harm to humans. Some vaccines, such as the diphtheria, tetanus, pertussis and hepatitis B vaccines, are made with a mercury-containing preservative called thimerosal. It is used to prevent bacterial contamination during production of the vaccine. The amount of thimerosal is 0.01% per dose, or 100 parts per million. This compound of mercury is not toxic to humans and does not release free mercury in the body. Any vaccine that is combined with inactivated polio vaccine (IPV), such as the DPT/IPV now used in Canada, does not contain thimerosal. Several vaccines (such as diphtheria and tetanus toxoids, and hepatitis B vaccine) contain a complex salt of aluminum called alum. The amount of aluminum is less than 1 mg per dose. This amount of aluminum is not known to cause any harm to humans. Much larger quantities of aluminum salts are taken and absorbed into the body in the form of antacids (e.g., 200­400 mg of aluminum hydroxide per tablet) without any serious side effects. Some vaccines contain trace amounts of antibiotics used during the manufacturing process. The purpose of the antibiotics is to prevent bacterial contamination of the tissue culture cells in which the viruses are grown. Measles, mumps and rubella (MMR) vaccine and inactivated polio vaccine (IPV) each contain less than 25 g of neomycin per dose (less than 0.000025 grams).

This document was published by the Canadian Paediatric society, 1997.

Posted by the Canadian Paediatric Society, July 1997.

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